# Copyright 2017 gRPC authors.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

import collections

def _threshold_for_count_below(buckets, boundaries, count_below):
  count_so_far = 0
  for lower_idx in range(0, len(buckets)):
    count_so_far += buckets[lower_idx]
    if count_so_far >= count_below:
      break
  if count_so_far == count_below:
    # this bucket hits the threshold exactly... we should be midway through
    # any run of zero values following the bucket
    for upper_idx in range(lower_idx + 1, len(buckets)):
      if buckets[upper_idx] != 0:
        break
    return (boundaries[lower_idx] + boundaries[upper_idx]) / 2.0
  else:
    # treat values as uniform throughout the bucket, and find where this value
    # should lie
    lower_bound = boundaries[lower_idx]
    upper_bound = boundaries[lower_idx + 1]
    return (upper_bound -
           (upper_bound - lower_bound) * (count_so_far - count_below) /
               float(buckets[lower_idx]))

def percentile(buckets, pctl, boundaries):
  return _threshold_for_count_below(
      buckets, boundaries, sum(buckets) * pctl / 100.0)

def counter(core_stats, name):
  for stat in core_stats['metrics']:
    if stat['name'] == name:
      return int(stat.get('count', 0))

Histogram = collections.namedtuple('Histogram', 'buckets boundaries')
def histogram(core_stats, name):
  for stat in core_stats['metrics']:
    if stat['name'] == name:
      buckets = []
      boundaries = []
      for b in stat['histogram']['buckets']:
        buckets.append(int(b.get('count', 0)))
        boundaries.append(int(b.get('start', 0)))
  return Histogram(buckets=buckets, boundaries=boundaries)
